This invention relates to an electric parts testing system and an electric parts testing method.
In the semiconductor testing process, a semiconductor testing system examines semiconductor devices or the like (hereinafter called DUT (device under test) as well) under test according to various predetermined conditions. Such a semiconductor testing system contains a number of electric parts such as a DUT board, performance board and motherboard for testing DUTs, etc. To ensure accurate measurement of DUTs, etc. by a semiconductor testing system, it is essential that those boards and other electric parts inside the semiconductor testing system operate accurately.
Some conventional semiconductor testing systems additionally contain self-diagnostic devices for testing their own electric parts contained in the systems.
Such self-diagnostic devices supply predetermined quantities of electric power at predetermined timings to individual electric parts inside the semiconductor testing system, or to selective portions of certain electric parts inside the semiconductor system, under predetermined test conditions. Thereafter, the self-diagnostic device observes outputs from those electric parts, or from the selective portions of the electric parts, and determines whether or not those outputs meet predetermined result conditions. If any of the outputs does not meet its result condition, then the self-diagnostic device notifies the user that the corresponding electric part did not satisfy the result condition. In other words, the self-diagnostic device notifies the user that the electric part was judged to be defective.
A number of test conditions are usually related to different test items to distinguish the conditions from each other. Therefore, in most cases, the self-diagnostic device notifies the user of a defective electric part by means of a test item instead of describing its test condition. Then the user can know the test condition used upon judgment of a defect or fault from the test item.
In general, a plurality of test conditions are related to each electric part. Therefore, when a certain electric part is defective, its defectiveness may be pointed out in more than one test item. Similarly, a single test item relates to the defectiveness of a plurality of parts. Therefore, even with a judgment of defectiveness for a test item and a test condition, it is difficult for the user to know which electric part is actually defective.
Such a self-diagnostic device was heretofore contained in a semiconductor testing system. Then, data on the causes of the defectiveness, test items and test conditions connected to the past judgment of defectiveness were stored. The self-diagnostic device showed the user the actual testing results of a particular electric part selected from the data as having been most often judged to be defective according to a selected test item.
However, the electric part most often judged to be defective by a single test item was typically a low quality electric part or a part more commonly used in a semiconductor testing system as compared with other electric parts. In other words, among various kinds of electric parts that otherwise have the same rate of defectiveness, the electric parts used most in the semiconductor testing system were more likely to become defective than the less commonly used electric parts. In addition, electric parts inferior in quality were also more likely to become defective than the other electric parts.
Heretofore, therefore, the self-diagnostic device always showed the user the most commonly used electric part in the semiconductor testing system or a poor quality electric part as being most likely the cause of defectiveness.
As stated above, in general, each electric part is related to a plurality of test items or test conditions, and each test item or test condition is related to a plurality of different electric parts.
In some cases, the electric part that is the actual cause of defectiveness can be a less commonly used electric part in the semiconductor testing system. In other cases, electric parts having been regarded previously as poor quality parts may have been improved in quality and seldom become defective.
If the self-diagnostic device makes judgments on a cause of defectiveness for a single test item in those cases, it will erroneously show the user an electric part that it is not the true cause of defectiveness.
Further, a long period of time was required for the self-diagnostic device to accumulate and be able to use data of actual results of the past causes of defectiveness and actual results of electric parts that have been causes of defectiveness. Therefore, it took a long time after initial use of the semiconductor testing system until data on actual results became available for actual use.
Moreover, once an electric part in its normal condition was misjudged to be the cause of defectiveness, it took a long time to detect the truly defective electric part.
It is therefore an object of the invention to provide, from the initial use, an electric parts testing system and an electric parts testing method capable of bringing to user""s attention an electric part with higher probability of being the cause of defectiveness than the conventional one
It is another object of the invention to provide an electric parts testing system and an electric parts testing method capable of detecting the truly defective electric part more quickly than the conventional technique after defectiveness is found by a test of electric parts.
An electric parts testing system comprises a testing unit to test electric parts for individual condition identifiers assigned for identification of a plurality of test conditions different from each other;
a first memory unit which previously stores estimated causes in relation at least to each said condition identifier, said estimated causes being obtained by estimation as causes of defectiveness of the electric parts;
a second memory unit to store at least one or more of the condition identifiers regarded as fault-connected identifiers when any of the electric parts are judged to be defective; and
an arithmetical unit to calculate a parameter when there are a plurality of said fault-connected identifiers, said parameter being related to the fault-connected identifiers at least for each said estimated cause related to the fault-connected identifiers.
Said parameter is preferred to the number of fault-connected identifiers related to said estimated causes.
Said parameter is preferred to the sum of expected values indicating how often each said estimated cause is estimated to be the cause of defectiveness, or the sum of probabilities of the past causes of defectiveness, said sum being obtained for each said fault-connected identifier.
The electric parts testing system is preferred to further comprise a display unit to display at least one or more of the estimated causes having the largest or smallest parameter value.
The electric parts testing system is preferred to further comprise a display unit to display a matrix of said estimated causes and said fault-connected identifiers to show which of the estimated causes is related to which of the fault-connected identifiers.
Each estimated cause is preferred to be related to expected data obtained by estimation of the nature of the electric part or the test condition, or data on actual results estimated on the basis of the actual past causes of defectiveness, said data on actual results being automatically renewed upon every calculation by the arithmetical unit.
An electric parts testing system includes a server system and a client system capable of exchanging data by mutual communication, comprising:
a testing unit contained in the client system, said testing unit testing electric parts for individual condition identifiers assigned for identification of a plurality of test conditions different from each other;
a first memory unit contained in the server system, said first memory unit previously storing estimated causes in relation at least to each said condition identifier, said estimated causes being obtained by estimation as causes of defectiveness of the electric parts;
a second memory unit contained in the client system, said second memory unit storing at least one or more of the condition identifiers regarded as fault-connected identifiers when any of the electric parts are judged to be defective;
an arithmetical unit contained in the server system, said arithmetical unit calculating a parameter when there are a plurality of said fault-connected identifiers, said parameter being related to the fault-connected identifiers at least for each said estimated cause related to the fault-connected identifiers; and
a display unit contained in the client system, said display unit displaying at least the parameter for each said estimated cause,
wherein the server system receives the fault-connected identifiers transmitted from the client system and transmits to the client system said parameter and said estimated causes related to the fault-connected identifiers.
The display unit is preferred to display a result display region for displaying result information of the tests having a plurality of said fault-connected identifiers, and the display unit displays a transmission command region for transmitting the result information displayed on the result display region to the server system in response to an operation of the client system, and after transmission of the result information to the server system, the display unit displays at least the parameter sent from the server system and the estimated causes related to the fault-connected identifiers.
The client system is preferred to transmit a transmitter identifier together with the result information in response to an operation of the client system, said transmitter identifier identifying the client system supplied with the result information from the server system.
The operation of the client system is preferred to be a selection of the transmission command display through an input device that can communicate with the client system.
An electric parts testing method to test electric parts for individual condition identifiers assigned for identification of a plurality of test conditions different from each other, comprises:
a first storage step of previously storing estimated causes in a memory, said estimated causes being obtained by estimation as causes of defectiveness of the electric parts and being related at least to each said condition identifiers;
a second storage step of storing in memory at least one or more of the condition identifiers regarded as fault-connected identifiers when any of the electric parts are judged to be defective;
an arithmetical step of calculating a parameter related to the fault-connected identifiers, said parameter being calculated at least for each said estimated cause related to the fault-connected identifiers when there are a plurality of said fault-connected identifiers.
The parameter calculated in the arithmetical step is preferred to be the sum of expected values indicating how often each said estimated cause is estimated to be the cause of defectiveness, or the sum of probabilities of the past causes of defectiveness, said sum being obtained for each said fault-connected identifier.
The electric parts testing method is preferred to further comprise a display step of displaying at least one or more of the estimated causes having the largest or smallest parameter value.
The estimated cause is preferred to be related to expected data obtained by estimation from the nature of the electric part and the test condition, said estimated cause being replaced by data on actual results estimated from the actual past causes of defectiveness.
The arithmetical step is preferred to includes:
a first arithmetic step of calculating a first parameter for each estimated cause, said first parameter being related to a plurality of the fault-connected identifiers; and
a second arithmetical step of calculating a second parameter for each estimated causes, said second parameter being related to a plurality of the fault-defective identifiers excluding predetermined one or more of the fault-connected identifiers.
The electric parts testing method is preferred to be executed on a server system and a client system which are prepared to exchange data by mutual communication,
wherein the server system executes the first storage step,
wherein the client system executes the second storage step,
wherein the client system executes a transmission step for transmitting a plurality of the fault-connected identifiers to the server system,
wherein the server system executes a receiving step for receiving the plurality of the fault-connected identifiers transmitted from the client system,
wherein the server system executes the arithmetical step, and
wherein the server system executes a return step for sending at least the parameter together with the estimated causes back to the client system, said estimated causes being related to the fault-connected identifiers.
Before the transmission step, the client system is preferred to execute a first display step of displaying at least a result display region for displaying a plurality of the fault-connected identifiers, and a transmission command region for transmitting the plurality of the fault-connected identifiers together with a transmitter identifier assigned to specify the client system,
wherein, in the transmission step, the client system is preferred to transmit data, which data are displayed in the result display region, to the server system in response to an operation of the client system, and
wherein, after the return step, the client system is preferred to execute a second display step for displaying the parameter sent back from the server system for individual estimated causes.
According to the invention, after defectiveness is found by a test of electric parts, an electric part more likely to be defective than a conventional one can be brought to user ""s attention.
Additionally, the invention can show the user an electric part with higher probability of being defective than conventional one from the initial use of the electric parts testing system.
Furthermore, according to the invention, after a fault is found by a test of electric parts, a truly defective electric part can be identified more quickly than with the conventional technique.